As commented before, the t_set_no_e2e_cancel_reason(1) should be used when handling the
INVITE.
In your case, you can use the workaround of removing the header and applying the changes,
so it is no header to propagate.
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Reply to this email directly or view it on GitHub:
https://github.com/kamailio/kamailio/issues/261#issuecomment-125496535